Method of separating wax and oil



Feb. 27, 1945. D NS ET-AL 2,370,453

METHOD OF SEPARATING WAX AND OIL Filed Feb. 28, 1942 WAX 27 33 050mm; SOLVENT- WAX AND NT AND ('sAs BUBBLES RED on.

HEAVY 01 L SOLUTION GASEOUS me AGENT JNVENTORSI E. M. DO N s O. G. MAURO BY mfiwifi l WQJ -ATTOR N EYS.

Patented Feb. 27, 1945 Eddie MfDons and Oswald G. Mauro, Tulsa,

Okla, assignors to Mid-Continent Petroleum Corporation, Tulsa, kla.,'. 'a' corporation of Delaware Application February 28, 1942, Serial No. 432,864 4 Claims. (Cl. 196-18) This invention relates to methods of separat ing wax and oil. The invention may be employed in separating wax and oil found in various kinds of materials including mineral oils, petrolatum, slack wax and vegetable Waxes. veniently used in dewaxing petroleum lubricating oils to produce low pour point lubricants, or in obtaining high melting point Waxes from petrolatum, and in separating constituents of slack wax, as well as in the treatment. of other products to separate waxy materials.

The main object of the invention is to'produ'ce a relatively simple and inexpensive system lacking several serious objections found in prior proc esses. The commercial development of this very old art has passed through a series of'stages,-

which eventually led to the modern dewaxing systems wherein extremely large filters are em ployed to separate wax from diluted oil.' Cold settling, using naphtha or the like as a diluent, is an old sluggish process, popular many years ago, but now practically abandoned and superseded by filtration.

Nevertheless, the highly developed conventional" filtering'processes now ingeneral use are complex systems, involving considerable trouble and expense, and lacking the desired efficiency in the separation of Wax from oil. In commercial practice, clusters of wax crystals are deposited on the filters with portions of the oil solution'trapped or.

systems which have been generally adopted in this industry.

A specific object of the present invention. is to produce an entirely feasible dewaxing system wherein gas bubbles are deliberately employed to aid in the separation of wax and oil, We

realize that experts in this art have regarded the creation of bubbles as a nuisance or objectionable condition to be carefully avoided in the separation of wax and oil. However, a study of the plan herein set forth will show that we have established novel conditions wherein this radical departure from the usual practice is employed to obtain substantial advantages.

Instead of exercising precautions to avoid a possibility of slight bubbling, we have created cooperative conditions wherein rather intense It can be conbubbling is an outstanding factor tending to promote the separation of wax and oil. For example,

in our new system a continuous stream of gas bubbles may be combined with a dewaxing solution heavier than wax, so as to forcibly lift the relatively light wax in the heavy solution, and in adesirabl'e form of the invention, the production of gas may be deliberately resorted to for the purpose of' disintegrating the wax; This bub-' bling, resulting in forcible disintegration of the wax, is contrary to the generally accepted prac-' tices and theories in this art, but we have created a novel series 'of conditions wherein the departure from conventional theories is unexpectedly employed to dispose of perplexing old problems.. I

More specifically stated, the wax may be precipitated by-.cooling in a relatively heavy solution of oil' and dewaxing solvent, and then.transmitted. into a settling chamber, while discharging gas bubbles into the waxy mass in said chamber, thereby causing the wax to rise with the bubbles, so as to forcibly lift the wax in said heavy oil solution. The bubbles will positively increase the velocity-of the rising wax, and this is a highly important factor in commercial production, where the object is to avoid unnecessary time in separating the wax from the oil. When the gas bubbles are deliberately created and employed to forcibly lift the wax as herein described, the

relatively heavy oil solution is quickly dewaxed, and a continuous stream of the heavy dewaxed solution may be discharged from a low portion of the separating chamber, While a continuous stream ofthe rising wax is discharged from an upper portion of said chamber. The bubbling is thus employed to select and readily separate a rising mass of light wax from the descending body of relatively heavy oil solution. This Silll from numerous vdiiferent normally gaseous ma terials, including carbon dioxide, sulfur dioxide, methane, ethane, hydrogen, or any other suitable normally gaseous materiah The normally gaseous material may be injected directly into the dewaxing'chamber as a separate stream, or it may enter with a stream of the waxy mixture .to be separated, and it may be combined with wax, it may be advantageously added before the:

oil solution reaches the coolingzone. A special advantage is gained by. including portionsof the-= normally gaseous material in the. precipitated. wax'clusters, as a subsequent expansion ofthis. normally gaseous material .in the-. waxnclustersi will have a sudden explosive force which forcibly disintegrates the wax clusters,-, thereby positively releasing the oil solution trapped iii the wax.

The liberated oil solution will then be free t'os I separate from thewax in the dewaxing or. de

oilingoperation. This is; a" substantial advantage, over the. usual" commercial practice; wherein" trapped or occluded oil is inevitablyretaine'di within ana between" wax clusters deposited" on the filters;

in. considering .the efi'ectilof the liberated gas is.. toIbe. .understoodltha't .the. invention compre- I hendsr, changes, variations and. modifications.

withinthescopeoi theclaims hereunto. appended}.

The accompanyinggdrawing .is. a .diagrammati-L cal view of asystemrwhich maybe employedilto carry-out one term oftheinventiom I A. continuous: regulated stream of; the waxbearing chargingistock, forijexamplei. a mama-.-

gm oilstock'; enters..the. fsystem through. a: ip

I which maybe provided.with:.a...purnp .21.and. aregulating valve 3. A continuous stream ar se-- -lective.dewaxingsolverit, from sources tobeheree after. described,.is..conducted ;througha pi 41 to the..oil supply pipe. 1 Thecontinuous streams. of. oil. and. dewaxing solvent are; united .in the. pipe -I and transmitted .through-..,a mixing nozzle. 5--.-where :the oil .andasolvent are; mixed at awteme. peratu-re: high enough to form the. desired dewaxingssolution. a a

The continuous stream... of solution. is trans This separating chamber 9 may be termed a dewaxing chamber, or settling chamber. The incoming stream of cooled solution and wax may be delivered to this chamber at approximately the temperature selected for precipitation of Wax in the cooler, or chiller, 6. For example, in dewaxing-lubricating oils this-temperatureymay be about .0"*F':., although higher. and lowertemperatures may be employed in separating various kinds of waxy materials. Ifhis chamber 9 is covered with insulation to aid in maintaining the desired temperatures therein.

We are. assuming that a relatively dense or heavy-- solvent has been selected for the dewaxing;operatiomiandsthat the viscosity and interracial tension areilow enough to allow the wax particlesto risein the dense solution. In this event, the major portion of the dense solution wilL-move-downwardly to the bottom of the separating chamber 9, where it is discharged through a pipe I 3, said" pipe having: a" regulating valve" I 4 adjustedto regulate the flow therein; This cutgoingisolution is freeof waxiand it may be dis tilled in. any suitable manner to -remove the sol ventfromthe'dewaxedoili' l Itwill be'ob'served thata highly. valuablecorn' mer'cial advantage can be gained by a .rapi'dd'e' waxing"; operation wherein the: rising wax is" quickly' separated from. the descending" oil solu.-'-'

tion; and that a. further advantage" can" be'iob tained by a convenientcooperative' step' ofde oiling thewaxi" The d ewaxing. operationflincludes' the step" of discharging gas" bubbles; into the waxy mass n the separating chamber 9, thereby causing; the bubbles to cling to and rise with waxparticles in the"re1atively.heavy oil solution, so'as to forcibly lift'said wax particles in the heavy solution. The descending oil solution is thusvery' easily, quick- 1y, andl'economically dewaxed in the simple set tling, chamber 9, and immediately discharged" at mitteduthrough a-cooler, or chiller; l5.w 1r1ere. the:

flowing-solution is cooled to. a l-temperature. desired. for :precipitationof wax in :theliquidsolu-. tion.

chamber=9.. The'dischar'ge end of this svalve house ing may be surrounded "by a shell or baffle" Ill to.

prevent violent agitation. in moreremoteportions of said chamberISe, An elongated needlevalvel I v maybe employed towregulatethe disc hargeifrom arr orifice at the inner end of the: housing. 8-,. said valve having ,an operating;- handle l2 exposed: at the exterior of the separating chamber 9.

the bottom, while'relatively lighti waxxparticles are. boosted to the top of saidlchamber where they maybe dischargedwin'a continuous stream with the gas bubbles.

The. gas.,bubbles are produced by introducing: a stream. off. normally gaseous. dewaxing. agent into thesystem. To-more specifically explain thisv condition we have shown a supply. pipe 15" leadingjfrom a source of. normally. gaseous. dewaxingmateriaLi and aplump. lfifto in'iect said materialgintothe system The pipe .I5".leads to the. .pipe "I which conducts. the charging stock. into thesystem,..and a.valve llmay. be adjusted to regulate, or. prevent, ,the' delivery of said nor: mally gaseous} material to thepipel; Thesupply pipe. I 51 is also. providedlwitha .-.branch ll 8"le'ading. to; the pipe I; and a. second branch. 1 (Heading to theinterior of the separating chamber. 91'.-

shown. diagrammatically. in the drawing, the .pipe l9.may terminate inthe shellorbaffl l0, audit is provided witha control: valvel'llj' while the pipe IBA-is equipped with a valve. 2'l/to,control tirade-- livery. of .norma1ly gaseous material. to the .pipe. 11:. The. valves [1,. 2ll-and 2! can be settolselectively regulate. orcontrol. the delivery oi prede. terniinedouantitiesbithe normally gaseous ole-- waxing. agent to. the, desired point, or. points, .in. theiwaxymaterial...

If the selected normally gaseous..material has no substantial value. in. the precipitation 'ot'wax. at the cooler S it-may be introducedtthrough the branch. I 8 .tothe-pipe 'l'; .or through-branch I 91190 a point adjacent the discharge endof the valve housing 8.

However, when said normally gaseous material is present in the cooler 6, it will form part of the oil solution trapped in the clusters of precipitated wax, and the valve I I may be adjusted to provide for a reduction in the pressure of the mixture entering the dewaxing chamber 9. In this event, the trapped normally gaseous material will suddenly expand in the wax clusters, so as to forcibly rupture or disintegrate said clusters entering the chamber 9, thereby positively liberating the trapped oil solution in said chamber. This releases all of the heavy oil solution for the dewaxing operation in said chamber 9.

The dewaxing solvent from pipe 4 is preferably a continuous stream of relatively heavy normally liquid solvent delivered'through a pump 22 and valve 23. The continuous stream of charging stock issupplied through the pump 2,

and the continuous stream of normally gaseous dewaxing agent is delivered through the pump l6. These pumps can be regulated to provide a relatively high pressure on the incoming streams, while the valve II is adjusted to provide a sudden reduction of pressure on the mixed stream at the inlet of the dewaxing chamber 8.

Under these conditions, the normally gaseous dewaxing agent may enter the system in a liquid state, and thereafter expand into gas bubbles at the inlet of the dewaxing chamber, where the waxy mixture is discharged from the valve housing 8. Any suitable normally gaseous material -may be employed. Specific examples of a few of the suitable normally gaseous agents include carbon dioxide, methane, ethane, sulfur dioxide and hydrogen.

Attention is now directed to the separating zone, or dewaxing zone, established near the point where the incoming mixture of cooled solution and wax begins to separate in the cham-- ber 9. The bubbles tend to cling to surfaces of the wax particles which move upwardly and carry with them portions of the oil solution, in. cluding oily films and relatively free portions of the solution between the. rising wax particles. The major portion of the heavy oil solution freely descends to the bottom of the chamber 9, but a minor portion of this oil solution is carried upwardly with the rising wax, which is discharged from an upper portion of said chamber 9.

Therefore, as a supplement to the efiicient dewaxing operation herein claimed, advantages can be gained by subjecting this outgoing wax to a simple deoiling operation. For example, the wax may be transmitted through a counterflowing stream of selective oil solvent to dissolve and recover oil solution carried by the wax.

To illustrate a suitable condition of this kind, we have shown a tubular discharge member 24 through which a continuous stream of the waxy material is discharged from the upper portion of the dewaxing chamber, and a counterflow deoiling system including an insulated column 25 above said dewaxing chamber. The tubular discharge member 24 is surrounded by but separated from the lower portion of said column 25, so as to provide an annular well or settling compartment 26 around the tubular member 24.

The mass of wax rising from the tubular member 24 passes through a relatively heavy descending stream which may be produced by continuously introducing a stream of deoiling solvent through a, pipe 21 leading into the upper portion of the column 25. The pipe 2'! is equipped with a pump 28 and a regulating valve 29 adjusted to regulate the flow of the incoming deoiling solvent, as well as a variable cooler 30 regulated to control the temperature of this solvent stream. This temperature may be slightly higher than the temperature of the solution discharged from the cooler 6 to the dewaxing chamber 9. For example, if the dewaxing solution is chilled to a temperature of 0 F. in the cooler 6, the incoming deoiling solvent from the cooler 30 may be at a temperature of about 10 F. to about 15 F. By deliberately maintaining a temperature differential of this kind, the deoiling solvent will more effectively deoil'the wax.

' When a heavy deoiling solvent is employed, the stream of deoiling solvent from the cooler 30 will descend in direct contact with the rising stream of wax particles, so as to selectively dissolve the free portions of oil solution carried by the wax, and also forcibly scrub the oily films from the rising wax particles. This action may be aided by any suitable mechanical appliances. For example, the column 25 may be provided with alternating baflies including a series of rings 3| extending inwardly from the inner face of the column 25 and a series of central bafile members 32 arranged as shown in the drawing to produce an elongated tortuous passageway wherein the rising wax particles move back and forth in a zigzag course. The stream of selective deoiling solvent descends through the rising stream of wax particles, and the counterfiowing streams are divided into numerous layers of different specific gravities contacting with each other and advancing in intersecting paths as they fiow from one baffie to another. These bafties are preferably provided with upwardly inclined top and bottom faces to permit free movement of the rising wax particles. It will be observed that the rising layers of wax particles move upwardly while in contact with the upwardly inclined bottom faces of the baffles, and that said wax particles repeatedly intersect the descending solvent while rising from one upwardly inclined plane to another. A continuous stream of deoiled wax with a minor portion of the solvent may be discharged through a pipe 33 above the inlet for the deoiling solvent.

The inclined faces of the bafiles tend to prevent the wax particles from clinging to said baflies. However, any suitable mechanical means may be employed to prevent or limit the growing of wax crystals which might otherwise extend from the bottom faces of the bailles. For example, the central baffles 32 may be fixed to a slowly rotating shaft 34 so as to rotate with the shaft, and scrapers 35 may extend from the top faces of these rotary baffles to remove waxy material from the bottoms of the stationary baffle rings 3|. These stationary baffles may be likewise provided with scrapers 36 extending from their top faces to remove waxy material from the bottom faces of the rotating bafiles.

An interesting condition appears in the effective cleansing of the rising wax particles due to the forcible scrubbing and dissolving action of the selective deoiling solvent which repeatedly crosses the path of the wax in the deoiling zone. Attention is also directed to the condition at the lower portion of this deoiling zone where the descending solvent stream is diverted-from the interior of the dewaxing chamber 9. This defiection of the descending solvent is due partly to the upward force of the rising stream of wax particles aissuing from; the t top; of the tubular. member 243. and partlyvto the-descending current in the'psurroundingsettlingpompartmentih That lowermost-central; bafiler 322 also; tends. to deflect:

- the descendinggsolvent,toward the :compartment:

26:, Some-of; the-:waxparticles may; bet swept;

into the settling; compartment 26; but these a wax.

ing chamber 9; soxthe deoiling; solvent stream' which: descends: through the: settling; comparte ment 26 cdntainsonly; a-rsmall percentage of the original. Oily. Therefore; this reasonably: fresh, body. of selective oil solvent can be veryconvemiently used in the dewaXi-ngl stage: ofathe process. For. example, it? may, be continuously transmitted; from the bottom of-the settling compartment 26 through a pipe -31. and thence. through thepump 22, and valve 2 3i in the; pipe 4" leadingy'to the,- continuous incoming streampf wax-bearing oilin: the pipe I. l

The velocity "and; time of, thedeoi'ling. action may be regulated-t to dissolve practically: of the oil. carried by.- the .W-QJX; or any desired percentageof, oil may: be; discharged with the. wax; depend-- ing upon the commercial requirements.

It is to be understood thatlthetinventiontisnot limited to. thespecificarrangementslof cham bers and zones herein disclosed to. illustrate one. form of the invention andwthat any, suitable; heavy solvents may be employed to: produce the counterflow of wax and solvent; However, .a des sirable selective deoiling, solvent may be composed. of methylene "dichloride alone or combined; with a relatively small; percentage of wax-rejecting solvent; More. specifically stated, the incoming deoiling solvent .from pipe 21; may consist of about 90- per; cent. methylene dichloride and: about ,10 per centdichlorethylether-or sul:- fur dioxide. Continuing; this specific illustration we find that: the, used deoiling:solvent:.and1 the I oil'dissolved thereby-maybe dischargedthrough pipes 3-| and 4-, to the. incoming.-- stream. of' oil; To pro ducea desirable selective 'dewa-xing. solvent composition, aregulated quantity ofewax-rejeot ing solvent may be a'd'dedintany suitable manner before the streamreaches-the cooler 6: FOI'WEX? ample, the normally-gaseousdewaxing agent-iron pipe l may, have wax-rejectingproperties. Such properties arefound immethane; ethane parbon dioxide, sulfur dioxide; andothen normally: gase ous materials. l M

Other examples of: the: relativelyheavy dewaxing solvents include; perchlorethylene: and: die chlorodifluoromethane;, either of which may: be combined with; a vvax rejecting: solvent to? pre'-- v cipitatewaxrin the-cooler--6.;

asap-ma;

in-, the systerm. The pump be employed to. maintain-rapa-rtial vacuumdn-the.separating system, on to compresssthe gas: asa stepri'n cone vertingt saidlga's into ,a liquidr When the zsystem istin service, there is a continuous: column. or liquid and wax extending} fromsthe, bottomof thedewaxing. chamber 9 to the upper end portion of the counterflow dee oiling. system, and .in a, very tall column of this kind, the head pressuremay. be great.-.enough tov prevent immediate vaporization of all of the normaily gaseous materialldischarged from the valvev housing 8;} Imsome cases, a portion of themora. mally gaseous material will be converted into-,-

, gas bubbles. under the; relatively high. pressure in the dewaxingchamber 9,- while other portions. of said. normally gaseous material will be successively converted into bubbles while rising:

through the higher zones zof gradually decreasing, pressure in the counterflown deoiling; zone. This successive bubbling at different elevationsyisea desirablecondition, tending to separate the wax particles for more effective deoiling, andalso tending. to increasethespeed .of the rising wax If the: used deoiling, solvent-is employed. in formingsthe dewaxing solvent, any dissolvedwax; willbe carried into the; incoming.charging-stock and-thereby recovered in. the system.- Another advantage of. this feature appears: m. the, con-- venient recovery ofvaluable oil which is constantlycarried by the selectivedeoili ng solvent flowing; from thedeoiling-zone to .the incoming charging stock, s 1

, We claim: 1. In the art of separating wax from oil wherein. the wax is'precipitatedin a cooledsolution of oil andnormallyliquid dewaxing-solventheav-v ier than. wax, the improvement vwhich comprisesadding aliquefied normallygaseous devvaxing agent under pressureto'the relatively heavy oil solution, causingsaidheavy oil solution to settlefrom the lighter wax in; a dewaxing chamber,v reducing. said, pressurerandthereby liberating" said normally,gaseousr-dewaxingagentintheform of bubbles intthe wax; so as;todisintegrateandforcibly: lift. the wax in said heavy oil solution, the step of reducing the pressure beingiperformed in the cooled solution before the precipitatedgvax separates from said solution, discharging :a. continuous stream of said dewaxed oil solution from= av relatively low portion ofsaid dewaxingchamher, and discharging a waxystreamfroma higher. portionrof said chamber. 1

2.- In the art of separating wax from oil, the

method-which comprises precipitating.--wax-.-infa relatively. heavy= solution ofoil-and. solvent in a cooled precipitating, zone while trapping; per-- tions of the oil solution in: the precipitated wax, transmitting amixture-of the precipitatedwax; and heavier oil" solution away from--said-cooledprecipitatingzone and into. A a1 separating; cham her, said -mixture including-- anormally. gaseous. material,- l liberating a substantial portion of said. normally? gaseous materiallin the formrof bubblesin the waxy'massm said chamber to dis: integrate the wax-andrelease trapped oil solution: therefrom; causing;- disintegrated; wax particles to rise with thegasbubbles in said heavy ,oilsold-- tion,- so as. to forcibly lift saidwax particlesin theheavieroil solution; discharging a waxistreamfromianupper. portion otisaid chamber, and dis-. charging a stream :of the. heavy oil .=solutionfrom" alower. portion of; said: chamber.

31' .In the art-oi separating wax-fromz oil',, ,the;

method of dewaxing oil and deoiling the wax which comprises transmitting a stream of precipitated wax and heavier oil solution into a dewaxing chamber, while discharging gas bubbles into the waxy mass in said dewaxing chamber, thereby causing wax particles to rise with the gas bubbles in said relatively heavy oil solu- 4 tion, so'as to forcibly lift the wax in the heavy oil solution, discharging a stream of the heavy oil solution from a, lower portion of said dewaxing chamber, discharging a stream of wax with portions of the oil solution from an upper portion of said dewaxing chamber to a countercurrent deoiling system, causing the stream of wax to rise in said countercurrent deoiling system while transmitting a descending stream of relatively heavy deoiling solvent through the mass of rising waxparticles, thereby subjecting the rising wax to a selective deoiling operation, discharging the ,wax from an upper portion of said countercurrent deoiling system, discharging a stream of the used deoiling solvent with its dissolved oil solution from a lower portion of said countercurrent deoiling system, mixing a continuous stream of the used deoiling solution with a continuous stream of the waxy oil stock to be separated, and cooling the mixed continuous stream to precipitate wax therein, thereby forming the precipitated wax and heavier oil solution for the first mentioned stream.

4. In the. art of separating wax from oil, the method of dewaxing oil and deoiling the wax which comprises transmitting a stream of preoipitated wax and heavier oil solution into a dewaxing chamber, while discharging gas bubbles into the waxy mass in said dewaxing chamber,'thereby causing wax particles to rise with the gas bubbles in said relatively heavy oil solution, so as to forcibly lift the wax in the heavy oil solution, discharging a stream of the heavy oil solution from a lower portion of said dewaxing chamber, discharging a stream of wax with portions of the oil solution from an upper portion of said dewaxing chamber to a countercurrent deoiling system, causing the stream of wax to rise in said countercurrent deoiling system while transmitting a descending stream of relatively heavy, normally liquid deoiling solvent through the mass of rising wax particles, thereby subjeoting the rising wax to a deoiling operation, discharging the wax from an upper portion of said countercurrent deoiling system, discharging a stream of the used normally liquid deoiling solvent with its dissolved oil solution from a lower portion of said countercurrent deoiling system, mixing a continuous stream of the used deoiling solution with a continuous stream of the waxy oil stock to be separated, and cooling the mixed continuous stream to precipitate wax therein, thereby forming the precipitated wax and heavier oil solution for the first mentioned' stream, at the same time injecting a continuous stream of normally gaseous dewaxing agent into one of the continuous streams to provide the gas bubbles in said dewaxing chamber.

EDDIE'M. DONS. OSWALD G. MAURO. 

